The trial, which also measured the effects of matcha green tea on cognitive functions, reported no significant improvements post-supplementation.

Findings of the study were recently published in Plos One. ​ 

A total of 99 Japanese seniors aged 60 to 85 years old took part in the 12-month trial.

These seniors have either subjective cognitive decline, meaning self-reported confusion or memory problems that have worsened in the past 12 months, or mild cognitive impairment, which is the early stage of memory loss or cognitive ability loss.

During the study, they were randomised to take nine capsules of placebo or matcha green tea. The nine capsules were equivalent to two grams of matcha green tea powder.

Two grams of matcha green tea was given for the intervention group as this is the amount consumed in the traditional Japanese tea ceremony Tea Otemae.

Each daily serve of matcha contains 170.8 mg of catechin, 48.1 mg of theanine, and 66.2 mg of caffeine. These are components which have been shown in existing studies to support sleep and cognitive function.

There are also a variety of catechins present in the matcha green tea given.

This includes 105.3 mg of EGCG, 1.5 mg of gallocatechin gallate, 20.3 mg of epicatechin gallate, 0.1 mg of catechin gallate, 33.1 mg of epigallocatechin, 1.6 mg of gallocatechin, 8.1 mg of epicatechin, and 0.8 mg of catechin.

Japanese beverage company ITO EN provided the trial materials.

The seniors’ sleep quality was assessed using the Pittsburg Sleep Quality Index (PSQI) scores, with lower score indicating better sleep quality.